This invention relates to a lens unit and a photographing apparatus, and relates in particular to a lens unit equipped with a zooming mechanism of a bending optical system.
In recent years, as personal computers have become more widely used, digital cameras in which images can be easily taken in to personal computers have also become widespread. In addition, it is becoming commonplace for digital cameras to be incorporated into information processing devices such as mobile computers, cellular phones, and personal digital assistants (PDAs). As digital cameras have become more widespread, there has been a desire for more compact digital cameras, and the lens unit needs to be even more compact. There is also a demand for a high magnification zoom lens and a zooming mechanism that can be used with the high magnification zoom lens is needed.
Thus, an example in which the barrel for holding the lens is telescopically stored in order to make the lens unit more compact is a movable frame posture restraining mechanism which includes a stationary main frame; a movable frame that is inserted telescopically into the stationary frame and which can move back and forth to the stationary main frame along the direction of an optical axis; a first shaft that is formed of two first pins which are orthogonal in the direction of movement of the movable frame and which coaxially project from the outer peripheral surface of the movable frame to the opposite sides at substantially 180° with respect to each other; a second shaft that is formed of two second pins which are orthogonal in both the direction of movement of the movable frame and the direction in which the first shaft extends and which coaxially project from the outer peripheral surface of the movable frame to the opposite sides at substantially 180° with respect to each other; a first holding mechanism which has two arms that are formed with one end supported so as to be swingable about the parallel axis in the direction of extension of the first pin and which engages with the first shaft at the swing tip side, and which holds the first shaft during movement of the movable frame and keeps the perpendicular posture of the first shaft with respect to the direction of movement of the movable frame; and a second holding mechanism which has two arms that are formed with one end supported so as to be swingable about the parallel axis in the direction of extension of the second pin and which engages with the second shaft at the swing tip side, and which holds the second shaft which is to prevent rotational movement of the first shaft of the movable frame which occurs due to movement of the movable frame and keeps the orthogonal posture of the second shaft with respect to the first shaft (Refer to Unexamined Japanese Patent Application Publication No. 11-119078).
In addition, there is a camera in which the lens barrel is formed from three units which include the stationary barrel which forms a portion of the camera body; the middle barrel which is stored telescopically inside the stationary barrel; and the movable barrel which is also stored telescopically inside the middle barrel, and the inner surface of the stationary barrel has a two-group type zoom device on which a helicoid groove is formed. More specifically, the engagement portion provided on the end portion of the middle barrel is engaged with the helicoid groove. The middle barrel can rotate in both normal and reverse directions via a gear mechanism using a direct current motor, and it moves telescopically with respect to the stationary barrel by the rotation. Further, the helicoid grooves are also formed on the inner surface of the middle barrel and the engagement portion of the end portion of the movable barrel engages with the helicoid grooves. The movable barrel cannot rotate with respect to the stationary barrel and thus when the middle barrel is rotated, it moves telescopically in the same direction as the telescopic movement of the middle barrel (See Unexamined Japanese Patent Application Publication No. 06-324247).
It is to be noted that the lens barrel is telescopically stored and the state of being stored inside the camera body is called collapsed.
However, in the posture restraining mechanism of the movable frame described in Japanese Patent No. 3666207, a structure is described in which one movable frame can move with respect to the stationary main frame, but in order to be usable with the high magnification zoom lens of recent years, it is necessary, for example, to increase the length of the arm portion in order to match the zooming mechanism which moves the zoom lens group toward the object side in large dimensions that is closest to the object of the zoom lens and it thus difficult for the length of the arm to be made compact corresponding to the reduced size of the zoom lens. Moreover, there is no disclosure with regard to two or more movable frames.
In addition, the two-group type zooming device described in Unexamined Japanese Patent Application Publication No. 06-324247, is a three unit structure, but it is necessary to form helicoid grooves on the inner surface of the stationary barrel and the middle barrel, and it is also necessary to form helicoid grooves on the end outer surface of the middle barrel and the end outer surface of the movable barrel which engage with these, and thus the mechanism becomes complex. Further, the barrels must be cylindrical because they have helicoid grooves. For this reason, the lens barrel which should correspond to the reduced size resulting from recent zoom lens cannot be made square to match the square shape of the image pickup element.
The present invention was conceived in view of the foregoing and an object thereof is to provide lens barrel which has a compact multilevel collapsing is possible with a simple structure and a photographing apparatus which comprises this lens barrel.